SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '736891c5107fb497948217ef772a10e38dac72f03b5834d84959fd33caf14cab' 
  AND token = 'O/9cpjDv8HqRhcvWAJ+9GMa5BGCK3rV3DnkaQaRnPq4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}